This invention relates in general to devices for supplying gas under pressure particularly for medical services and in particular to a new and useful gas dosing device for medical apparatus.
The gas dosing device can be used for medical apparatus wherever electrical control signals exist. The gas flow required there should be adjustable from 0.01 to 20 l/min.
A known arrangement for the electrically controlled dosing and mixing of gases contains in each feed line of the gases upstream of the mixing point a quick-action pilot valve. The pilot valves are on-off valves whose gas passage in the open state in dependence on two existing pressure difference is known. They are electrically controlled by a regulator which contains an arithmetic unit. A pressure converter is arranged in each feed line head of the pilot valve and in the common mixed-gas line and it is connected with the regulator.
Based on the known characteristic value, the measured pressures, as well as the given values for flow and mixing ratio, the regulator controls the passage of the pilot valves in a time slot pattern from which the desired dosing and mixing is obtained (German AS 29 31 856).
By using only one gas, the arrangement could still be used as a strict dosing device. But determining the dosing would require an elaborate quick-action computer which integrates the changing gas passage within the individual pulse. The gas pulses within this dynamic process have transient effects which limit the accuracy of the volume dosing.